Optical recording medium, optical recording medium producing apparatus and optical recording medium producing method

ABSTRACT

The present invention provides an optical recording medium, in which levels of wobble signals extracted from a recording area formed snakily, a reproduction exclusive area and an impossible area are maintained constant. On DVD-RW, groove tracks are snakily formed on a groove section on which recording information is recorded, and pit strings where a plurality of phase pits wave are arranged on the impossible area and the reproduction exclusive area which prevent illegal copying. On the respective areas, pit depths (groove depths), duty of the pit strings and wobbling amplitudes are set according to predetermined conditions so that the output levels of the wobble signals extracted based on the wobbling amplitudes can be maintained constant on the respective areas. As a result, synchronous control can be made accurately at the time of recording and reproduction on/from the DVD-RW.

BACKGROUND OF THE INVENTION

[0001] 1. Field of the Invention

[0002] The present invention relates to an optical recording medium suchas DVD, and particularly relates to an optical recording medium in whichrecording tracks are formed meanderingly.

[0003] 2. Description of the Related Art

[0004] In recent years, DVD is used as an optical information recordingmedium with large capacity generally and widely. In addition toRead-only DVD (DVD-ROM), the standard of DVD-RW (DVD-Re-recordable)being capable of recording and reproducing recording information isbeing laid down. Groove tracks are formed as recording tracks in apredetermined pattern on an optical disc according to the DVD-RWstandard. The groove tracks are formed meanderingly so as to be wobbled,and a wobble signal with constant frequency is extracted at the time ofrecording so as to be capable of being used as a reference signal whichsynchronizes with rotation of the DVD-RW.

[0005] Meanwhile, since recording is possible on DVD-RW, for example,various contents data recorded on DVD-ROM can be illegally copied ontoDVD-RW. Contents such as images and music are normally subject toprotection of their copyright, and it is requested that illegal copyingonto DVD-RW is prevented by a certain method and the copyright isprotected effectively.

[0006] Therefore, in the standard of DVD-RW (Ver.1.0), measures forpreventing illegal copying is defined, namely, predetermined data arepreviously embedded as emboss pit string (phase pit string) into an areaof DVD-RW corresponding to a recording area of DVD-ROM wherereproduction control data or the like were recorded. As a result, evenif other reproduction control data are overwritten on this area, areproduction signal of the overwritten data interferes with thereproduction signal of the emboss pit string so as not to be read, andthus other reproduction control data cannot be substantiallyoverwritten.

[0007] However, since the area into which the emboss pit string wasembedded is equal to that grooves are formed intermittently, an outputlevel of a wobble signal extracted from this area is lower than anoutput level of a wobble signal extracted from an area of a continuousgroove where recording data are recorded, and thus synchronous detectionof DVD-RW cannot be executed stably.

SUMMARY OF THE INVENTION

[0008] The present invention is devised in order to solve the aboveproblems and it is an object of the present invention to provide anoptical information recording medium which is capable of alwaysmaintaining a wobble signal based on wobbling of groove tracks in aconstant level and realizing stable synchronous control.

[0009] The above object of the present invention can be achieved by anoptical recording medium of the present invention onto which recordinginformation can be recorded optically. The optical recording medium isprovided with: a first area where the recording information is recordedon groove tracks formed meanderingly so as to extract wobble signal; asecond area where a phase pit string corresponding to control datarequired for reproduction control of the recording information isarranged meanderingly, the phase pit string having a pit depth so thatit enables the control data to be read and reading of other dataoverwritten on the phase pit string is prevented; and a third area wherea phase pit string corresponding to predetermined data is arrangedmeanderingly, the phase pit string having a pit depth so that it enablespre-pits including address information representing a recording positionon said optical recording medium to be read and reading of other dataoverwritten on the phase pit string is prevented. In addition, ameandering amplitude of said second area and a meandering amplitude ofsaid third area are set so that output levels of wobble signalsextracted from said respective areas are approximately equal to anoutput level of the wobble signal extracted from said first area.

[0010] According to this invention, by using the optical recordingmedium, the recording information is recorded on the first area and aplurality of phase pits are formed on the second and third areas so asto prevent illegal copying. At this time, since the respective areashave waving forms, the wobble signals can be extracted. On the secondand third areas, even if the pit depths are different from each other,since the wobbling amplitudes are set suitably, the output levels of thewobble signals which are substantially equal to the case of the firstarea as a reference can be obtained. Therefore, the output levels of thewobble signals can be always maintained constant on the different areasof the optical recording medium so that accurate synchronous control canbe utilized.

[0011] In one aspect of the present invention, the pre-pits are formedat least on said first area and said third area.

[0012] According to this aspect, the pre-pits are formed on the areasother than the second area. Therefore, even in the case where the phasepits on the second and third areas are formed into different pit depths,the output levels of the wobble signals can be maintained equal asmentioned above.

[0013] In another aspect of the present invention, the pit depth on saidthird area is set so as to be equal to the depth of the groove tracks ofsaid second area.

[0014] According to this invention, the depth of the groove tracks onthe first area is equal to the pit depth of the third area. Therefore,the output levels of the wobble signals from the first area and thethird area can be maintained equal as mentioned above only by changingthe waving amplitudes.

[0015] In further aspect of the present invention, on said first area, adepth of the groove tracks is set to 30 nm, on said second area, the pitdepth is set to 80 nm, an average duty of the pit string is set toapproximately 50%, and the meandering amplitude is set to beapproximately 2.7 times as much as that of said first area, and on thethird area, the pit depth is set to 30 nm, an average duty of the pitstring is approximately 80%, and the meandering amplitude is set to beapproximately 1.3 times as much as that of said first area.

[0016] According to this invention, suitable design conditions can begiven particularly in the case where DVD-RW is used.

[0017] In further aspect of the present invention, the meanderingamplitude of said third area is set so as to be equal to the meanderingamplitude of said first area.

[0018] According to this invention, the waving amplitude of the firstarea is equal to the waving amplitude of the third area. Therefore, theoutput levels of the wobble signals can be maintained equal as mentionedabove only by changing the depth of the groove tracks on the first areaand the pit depth of the third area.

[0019] In further aspect of the present invention, on said first area, adepth of the groove tracks is set to 30 nm, on said second area, the pitdepth is set to 80 nm, an average duty of the pit string is set toapproximately 50%, and the meandering amplitude is set so as to beapproximately 2.7 times as much as that of said first area, and on saidthird area, the pit depth is set to 50 nm, an average duty of the pitstring is set to approximately 80%, and the meandering amplitude is setto be equal to that of said first area.

[0020] According to this invention, suitable design conditions can begiven particularly in the case DVD-RW is used.

[0021] The above object of the present invention can be achieved by anoptical recording medium producing apparatus of the present inventionfor producing an optical recording medium onto which recordinginformation can be recorded optically using an optical disc master. Theapparatus is provided with: a first area forming device for cuttinggroove tracks meanderingly on said optical disc master using a lightbeam modulated by a wobble signal so as to form a first area onto whichthe recording information is recorded; a second area forming device formeanderingly cutting a phase pit string corresponding to control datarequired for reproduction control of the recording information on saidoptical disc master using the light beam modulated by the wobble signalso as to provide a pit depth which enables reading of the control dataand which prevents reading of other data overwritten on the phase pitstring, and for forming a second area; and a third area forming devicefor meanderingly cutting a phase pit string corresponding topredetermined data on said optical disc master using the light beammodulated by the wobble signal so as to provide a pit depth whichenables reading of pre-pits including address information representing arecording position on said optical recording medium and which preventsreading of other data overwritten on the phase pit string, and forforming a third area. In addition, in said second area forming deviceand said third area forming device, a degree of modulation of the lightbeams due to the wobble signal is set so the output levels of wobblesignals extracted from said respective areas are approximately equal toan output level of the wobble signal extracted from said first area atthe time of reproduction from said optical recording medium produced byusing said optical disc master.

[0022] According to the present invention, the first area where thegroove tracks are cut, and the second area and the third area where aplurality of phase pits are formed are formed on the optical disc masterto be used for producing the optical recording medium. At this time,since the light beam to be used for forming the respective areas ismodulated by the wobble signal, waving patterns are formed. On thesecond area and the third area, even in the case where the pit depths tobe cut are different, since the degree of the modulation is setsuitably, the pits can be formed with waving amplitude approximatelysame as that of the first area as a reference. Therefore, in the opticalrecording medium which is producing by using a stamper, the outputlevels of the wobble signals from different areas can be alwaysmaintained constant so that accurate synchronous control can beperformed.

[0023] In one aspect of the present invention, said first area formingdevice and said third area forming device form the pre-pits.

[0024] According to this aspect, the pre-pits are formed on the firstand third areas. Therefore, even in the case where the phase pits on thesecond and third areas are formed into different pit depths according toexistence/non-existence of pre-pits, in the optical recording mediumwhich is produced by using the stamper as mentioned above, the outputlevels of the wobble signals from the different areas can be alwaysmaintained constant.

[0025] The above object of the present invention can be achieved by anoptical recording medium producing method of the present invention forproducing an optical recording medium onto which recording informationcan be recorded optically using an optical disc master. The method isprovided with: a first area forming process of meanderingly cuttinggroove tracks on said optical disc master using a light beam modulatedby a wobble signal so as to form a first area on which the recordinginformation is recorded; a second area forming process of meanderinglycutting a phase pit string corresponding to control data required forreproduction control of the recording information on said optical discmaster using the light beam modulated by the wobble signal so as toprovide a pit depth which enables reading of the control data and whichprevents reading of other data overwritten on the phase pit string, andof forming a second area; and a third area forming process ofmeanderingly cutting a phase pit string corresponding to predetermineddata on said optical disc master using the light beam modulated by thewobble signal so as to provide a pit depth which enables reading ofpre-pits including address information representing a recording positionon said optical recording medium and which prevents reading of otherdata overwritten on the phase pit string, and of forming a third area.In addition, at the second area forming process and the third areaforming step, a degree of modulation of the light beam due to the wobblesignal is set so that output levels of the wobble signals extracted fromsaid respective areas are approximately equal to an output level of thewobble signal extracted from said first area.

[0026] According to the present invention, the first area where thegroove tracks are cut, and the second area and the third area where aplurality of phase pits are formed are formed on the optical disc masterto be used for producing the optical recording medium. At this time,since the light beam to be used for forming the respective areas ismodulated by the wobble signal, waving patterns are formed. On thesecond area and the third area, even in the case where the pit depths tobe cut are different, since the degree of the modulation is setsuitably, the pits can be formed with waving amplitude approximatelysame as that of the first area as a reference. Therefore, in the opticalrecording medium which is producing by using a stamper, the outputlevels of the wobble signals from different areas can be alwaysmaintained constant so that accurate synchronous control can beperformed.

[0027] In one aspect of the present invention, the first area formingprocess and the third area forming process form the pre-pits.

[0028] According to this aspect, the pre-pits are formed on the firstand third areas. Therefore, even in the case where the phase pits on thesecond and third areas are formed into different pit depths according toexistence/non-existence of pre-pits, in the optical recording mediumwhich is produced by using the stamper as mentioned above, the outputlevels of the wobble signals from the different areas can be alwaysmaintained constant.

BRIEF DESCRIPTION OF THE DRAWINGS

[0029]FIG. 1 is a plan view of DVD-RW according to an embodiment of thepresent invention;

[0030]FIG. 2A is a perspective view showing a structure of the DVD-RW onwhich pre-pits are formed;

[0031]FIG. 2B is a cross section view showing a structure of the DVD-RWon which pre-pits are formed;

[0032]FIG. 3 is an enlarged plan view showing a structure of areproduction exclusive area and an impossible area;

[0033]FIG. 4A is a cross section view showing a portion of thereproduction exclusive area where phase pits are formed;

[0034]FIG. 4B is a cross section view showing a portion of thereproduction exclusive area where phase pits are not formed;

[0035]FIG. 5 is a diagram showing one portion of a recording format inthe DVD-RW according to the present embodiment;

[0036]FIG. 6 is a diagram showing an experimental result correspondingto the present embodiment;

[0037]FIG. 7 is a block diagram showing a schematic structure of acutting device according to the present embodiment;

[0038]FIG. 8 is a flowchart showing a cutting process of an optical discmaster executed in the cutting device according to the presentembodiment;

[0039]FIG. 9 is a flowchart showing a process of forming a reproductionexclusive area in the cutting process of the optical disc masterexecuted in the cutting device according to the present embodiment;

[0040]FIG. 10 is a flowchart showing a process of forming an impossiblearea in the cutting process of the optical disc master executed in thecutting device according to the present embodiment;

[0041]FIG. 11 is a diagram showing an example of simulation whichobtains a relationship between output levels of tracking error signalsand pit depths (groove depths) in simulation results corresponding tothe present embodiment;

[0042]FIG. 12 is a diagram showing an example of simulation whichobtains a relationship between output levels of wobble signals andwobble amplitudes in the simulation results corresponding to the presentembodiment;

[0043]FIG. 13 is a diagram showing a structure of a first example of theDVD-RW according to the present embodiment; and

[0044]FIG. 14 is a diagram showing a structure of a second example ofthe DVD-RW according to the present embodiment.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0045] There will be explained below the preferred embodiments of thepresent invention with reference to the FIGS. 1 through 14. Here, theexplanation will be given as to embodiments in the case where thepresent invention is applied to DVD-RW as an optical recording medium onwhich recording information can be recorded.

[0046]FIG. 1 is a plan view of DVD-RW according to the embodiment and aplan view at the time of shipment of DVD-RW. As shown in FIG. 1, in aDVD-RW 1 of the embodiment, a clamp hole CH which is used for fixing toa spindle motor of an information recording apparatus (not shown) forrecording recording information onto the DVD-RW 1 on the shipment ismade at its center. Moreover, in the DVD-RW 1, a second area(reproduction exclusive area RA) into which an emboss pit stringcorresponding to control data required for reproduction control of therecording information is embedded, and a third area (impossible area UA)into which an emboss pit string corresponding to predetermined data isembedded are formed concentrically. According to the embodiment, thecontrol data can be read from the emboss pit string on the reproductionexclusive area RA, and the predetermined data cannot be read from theemboss bit string on the impossible area UA. As mentioned above, thereproduction exclusive area RA and the impossible area UA are areas onthe DVD-RW 1 which correspond to recording areas of the reproductioncontrol information or the like in DVD-ROM and prevent illegal copyingon the DVD-RW 1, and they are areas where another control data cannot beoverwritten.

[0047] In the case where recording information is recorded onto theDVD-RW 1 in the information recording apparatus, after an initializingprocess is first executed, a control information area RI, a lead-in areaL1 and a recording area DA as a first area of the present invention areformed on the DVD-RW 1 successively from an inner peripheral side asshown by a broken line in FIG. 1.

[0048] Control information which is used for recording and reproducingrecording information on/from the DVD-RW 1 is recorded onto the controlinformation area R1 at the time of initialization. Examples of theconcrete control information include setting information of intensity ofa light beam for recording and reproduction, and recording controlinformation to be used for recording. Starting information which showsstarting of recording and reproduction is recorded on the lead-in areaL1 at the time of initialization. The recording area DA is an area foractually recording recording information such as various contents on theDVD-RW 1. In FIG. 1, partition lines of the reproduction exclusive areaRA and the impossible area UA already formed at the time of shipment areshown by solid lines, and partition lines of the control informationarea RI, the lead-in area LI and the recording area DA to be formedafter initialization are shown by broken lines.

[0049] At the time when the initializing process on the DVD-RW 1 iscompleted, the reproduction exclusive area RA and the impossible area UAare included in the lead-in area LI. Moreover, when the recording of therecording information on the whole DVD-RW 1 is completed, a lead-outarea where end information showing completion of recording is formed onan outermost peripheral portion of the recording area DA.

[0050]FIG. 2 is a cross section showing a structure of the DVD-RW 1where pre-pits, mentioned later, are formed. FIG. 2A is a perspectiveview showing the structure of the DVD-RW 1 on the recording area DA, andFIG. 2B is a cross section that a groove track is viewed from adirection of an arrow in FIG. 2A.

[0051] In the DVD-RW 1, pre-pits 4 are formed on land tracks 3 in theareas except for the reproduction exclusive area RA at the time ofshipment. On the pre-pits 4, address information showing recordingpositions at the time of recording onto the DVD-RW 1 is recorded aspre-information.

[0052] In addition, the groove tracks 2 of the DVD-RW 1 are wobbled sothat a wobble signal which is used for synchronous control of the wholerecording operation such as rotation control is generated at the time ofshipment. Namely, the groove tracks 2 which wave at constant cycle arepreviously formed on the DVD-RW 1.

[0053] In FIGS. 2A and 2B, the DVD-RW 1 is a phase-changing type opticaldisc having a recording layer 11 composed of a phase-changing thin film,and the groove tracks 2 as recording tracks and the land tracks 3 asguide tracks which are adjacent to the groove tracks 2 are formed on asubstrate 9 alternatively. A light beam B with wavelength of 650 nm isemitted onto the groove tracks 2 at the time of reproduction orrecording, and the light beam B can be guided to the groove tracks 2 byfunction of the land tracks 3.

[0054] As shown in FIG. 2B, the groove track 2 has a cross sectionalstructure such that a resin layer 9A, a reflection layer 6, a protectivelayer 8, the recording layer 11, a protective layer 5 and a protectivefilm 7 are laminated in this order on the substrate 9. The protectivelayers 5 and 8 are arranged so as to sandwich the recording layer 11,and they protect the recording layer 11. The reflection layer 6 reflectsthe emitted light beam B. The protective film 7 and the resin layer 9Aare provided so as to protect the above respective layers from externalair and the like.

[0055] At this time, a depth of the groove track 2 is not less than 20nm to not more than 35 nm in the position of the recording layer 11, andan interval between center lines of the adjacent two groove tracks 2 is0.74 μM.

[0056] Meanwhile, as mentioned above, the pre-pits 4 corresponding tothe pre-information are formed on the land tracks 3 at the stage ofshipment. When the information recording apparatus records recordinginformation onto the DVD-RW 1, the pre-pits 4 are detected so that thepre-information previously recorded is obtained in a manner, mentionedbelow. An optimal output or the like of the light beam B is set based onthe pre-information so as to be recorded on a predetermined recordingposition of the recording information based on address information asthe pre-information.

[0057] In addition, as shown in FIG. 2A, the groove tracks 2 are formedmeanderingly so as to be wobbled. A wobble signal which is extractedbased on the wobbling of the groove tracks 2 is a periodic signal ofcomparatively low frequency (concretely, 140 kHz). Moreover, since awobbling amplitude as a waving amplitude of the groove tracks 2 ismaintained constant, the level of the extracted wobble signal becomesconstant. When the information recording apparatus records the recordinginformation onto the DVD-RW 1, the wobble signal is extracted from adetection signal of the groove track 2. This wobble signal is used as asynchronizing reference so as to control the whole operation of theDVD-RW 1.

[0058] Here, as shown in FIG. 2A, when recording information is recordedon the DVD-RW 1, the light beam B is emitted so that it traces a centerof the groove track 2, and phase-changing pits are formed into apredetermined pattern on the groove track 2 so that the recordinginformation is recorded.

[0059] At this time, the size of an optical spot SP formed by the lightbeam B is, as shown in FIG. 2A, set so that the optical spot SP isemitted onto the groove track 2 and a portion of the optical spot SP canbe emitted the land track 3. According to a push-pull method (a radialpush-pull method using a photo detector divided by dividing linesparallel with a rotational direction of the DVD-RW 1), a reflected lightof the optical spot SP is used and pre-information of the pre-pits 4 isdetected. Tracking servo control for letting the light beam B follow thegroove tracks 2 is also made by the push-pull method.

[0060] Next, there will be explained below a structure of thereproduction exclusive area RA formed on the DVD-RW 1 with reference toFIGS. 3 and 4. FIG. 3 is an enlarged plan view showing a structure inthe vicinity of a boundary between the reproduction exclusive area RAand the impossible area UA. FIG. 4A is a cross section view of thereproduction exclusive area RA taken along the line A-A′ of FIG. 3, andFIG. 4B is a cross section view of the reproduction exclusive area RAtaken along the line B-B′ of FIG. 3. Here, FIG. 4A is a cross sectionview corresponding to FIG. 2A, and FIG. 4B is a cross section viewcorresponding to FIG. 2B.

[0061] In the reproduction exclusive area RA, the continuous groovetracks 2 and land tracks 3 shown in FIG. 2 are not formed. Meanwhile, asshown in FIG. 3, a plurality of phase pits PI as the emboss pit stringfor reproduction control information or the like to be used forreproduction of the DVD-RW 1 are formed on the reproduction exclusivearea RA. The level of the reflected light changes because of diffractioncaused by the phase pits PI when the light beam B is emitted to the pitsso that existence or absence of the phase pits PI is discriminated andthe reproduction control information or the like can be detected.

[0062] As shown in FIG. 3, due to the phase pits PI formed on thereproduction exclusive area RA, the pit strings which are arrangedintermittently along the center line CL are arranged meanderingly, andthey are wobbled with constant period. A period that the pit strings ofthe phase pits PI meander is set similarly to the wobbling period of thegroove tracks 2 shown in FIG. 2. Moreover, a wobbling amplitude of thepit string of the phase pits PI is set suitably taking the level of thewobble signal into consideration as mentioned later. Also in the casewhere the pit string of the phase pits PI on the reproduction exclusivearea RA is traced, the wobble signal can be extracted.

[0063] Here, the depth of the phase pits PI on the reproductionexclusive area RA is set in a range of 60 nm to 90 nm in the position ofthe recording layer 11 so that the control data can be read and readingof another control data overwritten on the phase pit string isprevented. Moreover, an interval of the center lines of the phase pitsPI adjacent to each other in a radial direction of the DVD-RW 1 is setto 0.74 μm similarly to the case of the groove tracks 2. In the presentembodiment, the depth of the phase pits PI is set suitably so that thelevel of the wobble signal based on the pit string of the phase pits PIon the reproduction exclusive area RA becomes similar to the level ofthe wobble signal based on the wobbling of the groove tracks 2, but thedetails will be mentioned later.

[0064] Here, a portion on the reproduction exclusive area RA where thephase pits PI are not formed is completely a plane as shown in FIG. 4B.

[0065] In addition, the pre-pits 4 are not formed on the reproductionexclusive area RA. This is because, as mentioned later, the phase pitsPI and the pre-pits 4 are formed so as to have the same depth, and thuswhen both of them exist on one area, they optically interferes with eachother and the detection of them is difficult.

[0066] Next, there will be explained below a structure of the impossiblearea UA formed on the DVD-RW 1 with reference to FIG. 3. As shown inFIG. 3, the continuous groove track 2 and land track 3 are not formed onthe impossible area UA similarly to the reproduction exclusive area RA.Meanwhile, a plurality of phase pits PI′ as the emboss pit string areformed on the impossible area UA, and they correspond to predetermineddata 8-16 modulated. Moreover, the pit string of the phase pits PI′ iswobbled.

[0067] Here, a depth of the phase pits PI′ on the impossible area UA isset to be not less than 20 nm and not more than 35 nm in the position ofthe recording layer 11 so that the pre-pits 4 can be read and reading ofanother control data overwritten on the phase pit string is prevented,namely, this depth is similar to the groove tracks 2. In the case wherea light beam is emitted onto the recording layer 11 on the impossiblearea UA having such a structure so that phase-change pits are formed,due to interference with the phase pits PI′ above the phase-change pits,contents of the phase-change pits cannot be detected.

[0068] Here, address information is recorded on the impossible area UAby the pre-pits 4. Therefore, before the light beam B for recordingreaches the recording area DA according to the rotation of the DVD-RW 1at the time of recording, the recording position on the DVD-RW 1 can beknown in the information recording apparatus.

[0069] Next, there will be explained below a recording format in theDVD-RW 1 according to the present embodiment with reference to FIG. 5.FIG. 5 is a diagram showing one part of the recording format of theDVD-RW 1 after the lead-in area LI and the recording area DA are formed.

[0070] As shown in FIG. 5, after the above-mentioned initializingprocess is executed, an initial zone IZ, a reference code zone RZ, afirst buffer zone B1, the reproduction exclusive area RA, the impossiblearea UA and a second buffer zone B2 are formed on the lead-in area LI inthis order from its inner peripheral side. Zero data are recorded on allbit strings of the initial zone IZ, the first buffer zone B1 and thesecond buffer zone B2. Moreover, reference codes including the startinginformation or the like are recorded on the reference code zone RZ.

[0071] As shown on the left side of FIG. 5, the address information onthe pre-pits 4 is set so that the address information of the initialzone IZ, the reference code zone RZ and the first buffer zone B1 aresuccessively incremented from the inner peripheral edge. On thecontrary, the address information on the pre-pits 4 is set so that theaddress information of the impossible area UA and the second buffer zoneB2 are successively decremented from the innermost peripheral portion ofthe recording area DA (outermost peripheral portion of the second bufferzone B2). As mentioned above, since address information is not set onthe reproduction exclusive area RA where the pre-pits 4 are not formed,address information is set discontinuously before and after thereproduction exclusive area RA.

[0072] Meanwhile, sector numbers corresponding to the DVD format are setas shown on the right side of FIG. 5. Namely, the sector numbers arepreviously recorded on the reproduction exclusive area RA by the phasepits PI at the time of shipment. On the contrary, the sector numberswhich are continuously arranged after initialization are set on thelead-in area LI except for the reproduction exclusive area RA and theimpossible area UA. At this time, the sector numbers are set on theimpossible area UA so as to change continuously between its innermostperipheral portion and its outermost peripheral portion.

[0073] Next, there will be explained below a relationship between thedepth of the phase pits PI and optical characteristics on thereproduction exclusive area RA with reference to FIG. 6. FIG. 6 shows anexperimental result of a relationship among the depth of the phase pitsPI of the reproduction exclusive area RA and an output level of adetection signal detected from the phase pits PI and an output level ofa tracking error signal based on the push-pull method.

[0074] As mentioned above, in order to detect the sector information orthe like recorded by the phase pits while the tracking servo control isbeing accurately made on the reproduction exclusive area RA, it isnecessary to detect the detection signal and the tracking error signalat satisfactory output level. In FIG. 6, in order to set the outputlevels of the detection signal and the tracking error signal in theallowable range, it is necessary to set the depth of the phase pits PIto not less than 60 nm and not more than 90 nm (area B in FIG. 6).Moreover, when the depth of the phase pits PI is set to not less than 70nm to not more than 80 nm (area A in FIG. 6), the output levels of thedetection signal and the tracking error signal can be further optimized.

[0075] Next, there will be explained below a cutting device S forproducing the DVD-RW 1 having the above structure with reference to FIG.7. FIG. 7 is a block diagram showing a schematic structure of thecutting device according to the present embodiment.

[0076] As shown in FIG. 7, the cutting device according to the presentembodiment is composed of a land data generator 20, a parallel/serialconverter 21, a pre-format-use encoder 22, a clock signal generatingsection 23, a laser generating device 24, a light modulator 25, anobjective lens 26, a spindle motor 29, a rotation detector 30, arotational servo circuit 31, a feed unit 32, a position detector 33, afeed servo circuit 34, a CPU 40, a groove data generator 50, a wobblesignal generator 51, a variable gain amplifier 52 and a switch 53.

[0077] In addition, an optical disc master is composed of a glasssubstrate 27, and a resist 28 coated on the glass substrate 27. Theresist 28 is exposed to light beams BG and BL, mentioned later, and pitswhose forms correspond to changes in the intensity of the light beams BGand BL are formed.

[0078] In FIG. 7, the land data generator 20 outputs parallel datacorresponding to a pattern of the pre-pits 4 formed on the land tracks 3under control by means of CPU 40. The output parallel data are convertedinto serial data by the parallel/serial converter 21. The serial dataare input into the pre-format-use encoder 22, and a land data signal SLfor actually forming the land tracks 3 and the pre-pits 4 on the opticaldisc master is generated based on a pre-formatting clock signal suppliedfrom the clock signal generating section 23 so as to be output to thelight modulator 25.

[0079] Meanwhile, the groove data generator 50 generates groove datacorresponding to the groove track 2 or the patterns of the phase pits PIand PI′ to be previously formed under control by means of the CPU 40 soas to output the groove data as a control signal for the switch 53.

[0080] In addition, the wobble signal generator 51 generates a wobblesignal for wobbling the groove tracks 2. The wobble signal is amplifiedby the variable gain amplifier 52 according to predetermined wobble gainbased on control by means of the CPU 40 so as to be output to the switch53.

[0081] The wobble signal to which the gain was added and the grand levelare input into the switch 53, and switch control is performed based onthe groove data output from the groove data generator 50. As a result, agroove data signal SG for actually forming a format of the groove tracks2 on the optical disc master is output to the light modulator 25.

[0082] The laser generating device 24 emits a first light beam BG forforming groove tracks and a second light beam BL for forming pre-pits 4of the land tracks 3 onto the optical disc master. The light modulator25 modulates the first light beam BG based on the groove data signal SG,whereas modulates the second light beam BL based on the land data signalSL. Further, a laser power in the laser generating device 24 iscontrolled at predetermined timing according to control by means of theCPU 40. The light beams BG and BL are condensed on the optical discmaster via the objective lens 26.

[0083] At this time, the spindle motor 29 rotates the optical discmaster, and the rotation detector 30 detects rotation of the opticaldisc master. As a result, the rotation servo circuit 31 controls therotation of the optical disc master, and outputs a rotation pulse whichsynchronizes with the rotation.

[0084] The position detector 33 detects a position of the feed unit 32,and outputs the detection signal to the feed servo circuit 34. The feedservo circuit 34 obtains position information of the feed unit 32 basedon the detection signal from the position detector 33 so as toservo-control transfer of the feed unit 32.

[0085] When the above operation is performed, a convex-concave formcorresponding to spiral tracks and emboss pit string are formed on theoptical disc master so that a stamper disc as a trimming die forproducing an optical disc is formed based on the optical disc master.Thereafter, a replication process using the stamper disc is executed sothat the DVD-RW 1 as a replica disc of the present invention ismass-produced.

[0086] Next, there will be explained below the process of cutting theoptical disc master executed in the cutting device according to thepresent embodiment with reference to flowcharts in FIGS. 8 through 10.Here, this process is executed mainly by the CPU 40 according to controlprogram stored in a memory device (not shown).

[0087] As shown in FIG. 8, when the process in the cutting device isstarted, the wobble gain in the variable gain amplifier 52 and the laserpower in the laser generating device 24 are initialized (step S1). Here,the wobble gain in the case where the groove tracks 2 are formed with astandard wobbling amount is set, and the laser power is set so that thedepth of the groove tracks 2 becomes 30 nm.

[0088] Thereafter, the pre-pits 4 of the groove tracks 2 and the landtracks 3 are started to be formed on the optical disc master (step S2).Namely, while the rotation servo circuit 31 and the feed servo circuit34 are being controlled, the laser generating device 24 is driven sothat the first light beam BG and the second light beam BL are started tobe emitted onto the optical disc master.

[0089] Referring to the address information to be recorded on thepre-pits 4, it is determined whether or not the light beams reach thereproduction exclusive area RA (step S3). As shown in FIG. 5, when ahead address 002F20h of the reproduction exclusive area RA is detected,it is determined that the light beams reach the reproduction exclusivearea RA. As a result of the determination at step S3, when the lightbeams reach the reproduction exclusive area RA (step S3; YES), theprocess of forming the reproduction exclusive area RA is executed (stepS4).

[0090] There will be explained below the concrete process at step S4with reference to FIG. 9. When the process of forming the reproductionexclusive area RA shown in FIG. 9 is started, since the pre-pits 4 donot exist on the reproduction exclusive area RA as mentioned above, theforming of the pre-pits 4 is temporarily stopped (step S11). As aresult, the emission of the second light beam BL onto the optical discmaster by the laser generating device 24 is stopped.

[0091] Next, the wobble gain is set so as to conform to wobblingamplitude due to the pit string of the phase pits PI on the reproductionexclusive area RA (step S12). Moreover, the laser power is set so as toconform to the depth of the phase pits PI on the reproduction exclusivearea RA (step S13). The concrete setting of the wobbling amplitude andthe depth of the phase pits PI on the reproduction exclusive area RAwill be mentioned later.

[0092] Next, the sector number to be recorded by using the phase pits PIon the reproduction exclusive area RA is set to 002F200h (step S14). Asshown in FIG. 5, this corresponds to the head sector number of thereproduction exclusive area RA.

[0093] Next, the phase pits PI are started to be formed on thereproduction exclusive area RA (step S15). As a result, the pit stringof the phase pits PI is formed on the reproduction exclusive area RA soas to have predetermined wobbling amplitude and pit depth.

[0094] After step S15, referring to the above sector number, it isdetermined whether or not the first light beam reaches the impossiblearea UA (step S16). As shown in FIG. 5, when a sector numbercorresponding to the head address 002FD0h on the impossible area UA isdetected, it is determined that the first light beam reaches theimpossible area UA. As a result of the determination at step S16, whenthe first light beam BG reaches the impossible area UA (step S16; YES),the sequence goes to step S5 in FIG. 8.

[0095] Next, as shown in FIG. 8, the process of forming the impossiblearea UA is executed (step S5). There will be explained below theconcrete process at step S5 with reference to FIG. 10. When the processof forming the impossible area UA shown in FIG. 10 is started, since itis necessary to form the pre-pits 4 on the impossible area UA asmentioned above, an address to be recorded by the pre-pits 4 is set to002FD0h. As mentioned above, this corresponds to the head address on theimpossible area UA.

[0096] The recording of pre-pits 4 which is temporarily stopped at stepS11 is restarted (step S22). Hereinafter, the second light beam BL isemitted onto the optical disc master by the laser generating device 24.

[0097] Next, a wobble gain is set so as to conform to wobbling amplitudedue to the pit string of the phase pits PI′ on the impossible area UA(step S23). Moreover, a laser power is set so as to conform to the depthof the phase pits PI′ on the reproduction exclusive area RA (step S24).The concrete setting of the wobbling amplitude and the depth of thephase pits PI′ on the impossible area UA will be mentioned later.

[0098] Next, the phase pits PI′ on the impossible area UA are started tobe formed (step S25). As a result, the pit string of the phase pits PI′is formed on the impossible area UA so as to have predetermined wobblingamplitude and depth, and the pre-pits 4 for the address information areformed so as to be adjacent to the pit string.

[0099] After step S25, referring to the address information, it isdetermined whether or not the light beams reach the second buffer zoneB2 (step S26). As shown in FIG. 5, when a head address 002FE0h of thesecond buffer zone B2 is detected, it is determined that the light beamsreach the second buffer zone B2. As a result of the determination atstep S26, when the light beams reaches the second buffer zone B2 (stepS26; YES), the sequence goes to step S6 of FIG. 8.

[0100] Next, as shown in FIG. 8, the wobble gain and the laser powerwhich were changed as mentioned above are returned to the initial setstate similarly to step S1 (step S6). Hereinafter, the groove tracks 2with standard wobbling amount and depth of 30 nm are formed.

[0101] After step S6, referring to the address information, it isdetermined whether or not the light beams reach a predeterminedrecording end position of the DVD-RW 1 (step S7). As a result, when thelight beams reach the recording end position (step S7; YES), the cuttingprocess of FIGS. 8 through 10 is ended.

(Concrete Examples)

[0102] The present embodiment will explains concrete examples relatingto the reproduction exclusive area RA and the impossible area UA. In thefollowing examples, the wobbling amplitude and the pit depth withrespect to the pit strings of the phase pits PI and PI′ are parametersto be set suitably so that the output levels of the wobble signals onthe reproduction exclusive area RA and the impossible area UA areoptimized.

[0103] At first, there will be explained below a simulation resultrelating to the parameters and output characteristics of the wobblesignals with reference to FIGS. 11 and 12. FIG. 11 is an example ofsimulation obtaining a relationship between the pit depth (groove depth)and an output level of a tracking error signal based on the push-pullmethod. Moreover, FIG. 12 is an example of simulation obtaining arelationship between the wobbling amplitude and the output levels of thewobble signals.

[0104]FIG. 11 shows comparison of characteristics among a groove sectionwhere the groove tracks 2 are formed, and two kinds of pit stringscomposed of phase pits with duty of 80% and duty of 50% instead of thegroove tracks 2. Here, the three characteristics in FIG. 11 correspondto the case where the wobbling amplitudes have a constant value.Moreover, in FIG. 11, the axis of ordinates shows the output level ofthe tracking error signal, but since the output level of the wobblesignal is proportional to the output level of the tracking error signal,in the case where the axis of ordinates in FIG. 11 shows the outputlevel of the wobble signal, the similar curve is obtained.

[0105] The duty of the pit string represents an average value ofproportion of the phase pit formed portion of the length in the trackdirection. Since the reproduction exclusive area RA where the sectorinformation or the like is recorded has no degree of freedom in the pitarrangement, the duty is roughly assumed to be 50%. Meanwhile, on theimpossible area UA in which the pit arrangement is random, the duty canbe adjusted to a certain degree, and thus the duty is assumed to be 80%as a condition closer to that of the groove section. In the case of thegroove section, the duty can be considered as 100%.

[0106] As is clear from FIG. 11, in the case where the pit depths(groove depth) are the same, when the duties become smaller, the outputlevels become smaller. This is because the phase pit portions decreaseso that a phase change to be given to the emitted light beam is smaller.

[0107] In FIG. 11, the groove depth of the groove section is set to 30nm so that it conforms to the standard. Moreover, on the reproductionexclusive area RA, the depth of the phase pits PI is set to 80 nm in thesuitable range based on the optical characteristics shown in FIG. 6. Onthe contrary, taking the detecting performance of the pre-pits 4 intoconsideration, it is necessary to reduce the pit depth of the phase pitsPI′ on the impossible area UA. Here, the depth of the phase pits PI′ onthe impossible area UA is set to 30 nm and 50 nm. In FIG. 11, thepositions of these set pits depths (groove depths) are represented bydotted lines.

[0108]FIG. 12 shows a change in the output level of the wobble signalwhen the wobbling amplitude is changed in the case where the pit depths(groove depths) are set according to the above conditions. The casewhere depth of the phase pits PI′ on the impossible area UA is set to 30nm corresponds to condition A, and the case where it is set to 50 nmcorresponds to condition B.

[0109] As is clear from FIG. 12, the wobbling amplitudes areproportional to the output levels of the wobble signals. Moreover, evenif the wobbling amplitudes are the same so as to correspond to thecharacteristics in FIG. 11, the output levels of the wobble signals,which are extracted based on the condition B on the groove section andthe impossible area UA, the condition A on the impossible area UA andthe reproduction exclusive area RA become smaller in this order.Therefore, in the present embodiment, the wobbling amplitudes areadjusted so that lowering of the output levels of the wobble signals dueto a difference in the conditions shown in FIG. 12 is compensated.

[0110] There will be explained below two examples of the DVD-RWaccording to the present embodiment based on the above investigationwith reference to FIGS. 13 and 14. FIG. 13 is a diagram showing astructure of a first example, and FIG. 14 is a diagram showing astructure of a second example.

[0111] In the two examples shown in FIGS. 13 and 14, the condition ofthe groove sections and the condition of the reproduction exclusive areaRA are common. Namely, the groove depth is set to 30 nm, and thewobbling amplitude X is set to a predetermined amount which was presetas a standard. Moreover, the pit depth of the phase pits PI on thereproduction exclusive area RA is set to 80 nm, and the wobblingamplitude is set to 2.7 X under the condition that the duty is 50%.

[0112] In the first example shown in FIG. 13, the pit depth of the phasepits PI′ on the impossible area UA is set to 30 nm, and the wobblingamplitude is set to 1.3 X under the condition that the duty is 80%. Atthis time, as shown at the lower portion of FIG. 12, the output level Yof the wobble signal extracted from the groove section is similar to theoutput levels Y of the wobble signals extracted from the impossible areaUA and the reproduction exclusive area RA.

[0113] Next, in the second example shown in FIG. 14, the pit depth ofthe phase pits PI′ on the impossible area UA is set to 50 nm, and thewobbling amplitude is set to X under the condition that the duty is 80%.In this case, as shown at the lower portion of FIG. 13, the output levelY of the wobble signal extracted from the groove section is similar tothe output levels Y of the wobble signals extracted from the impossiblearea UA and the reproduction exclusive area RA.

[0114] In the first and second examples, the output levels of the wobblesignals on all the areas can be the same. In the first embodiment, onthe groove section and the impossible area UA, the pit depths (groovedepths) are commonly set to 30 nm. Meanwhile, in the second example, onthe groove section and the impossible area UA, the wobbling amplitudes Xare set commonly.

[0115] As mentioned above, according to the DVD-RW 1 of the presentembodiment, even in the case where the reproduction exclusive area RAand the impossible area UA for preventing illegal copying are provided,the conditions such as the pit depths and the wobbling amplitudes areset suitably, the output levels of the wobble signals based on therespective areas can be maintained constant. As a result, thesynchronous control at the time of controlling recording andreproduction using the wobble signals can be stabilized.

[0116] The present invention is not limited to the above-mentionedembodiments. For example, in the above embodiments, the DVD-RW is usedas the optical recording medium onto which recording information can berecorded optically, but the present invention can be applied to opticalrecording media such as DVD-R based on another formats.

[0117] In addition, according to the cutting device as the opticalrecording medium producing apparatus, the pre-pits 4 and the groovetracks 2 are cut on an optical disc master by different light beams BGand BL. However, one light beam is diffracted greatly in a radialdirection of a disc by the light modulator 25 so that the pre-pits 4 canbe formed. Moreover, according to the optical recording medium producingapparatus, the depths of the phase pits are changed by adjusting thepower of a light beam, but the depths can be changed also by controllingthe light modulator 25.

[0118] The invention may be embodied in other specific forms withoutdeparting from the spirit or essential characteristics thereof. Thepresent embodiments are therefore to be considered in all respects asillustrative and not restrictive, the scope of the invention beingindicated by the appended claims rather than by the forgoing descriptionand all changes which come within the meaning and range of equivalencyof the claims are therefore intended to be embraces therein.

[0119] The entire disclosure of Japanese Patent Application No.2000-224216 filed on Jul. 25, 2000 including the specification, claims,drawings and summary is incorporated herein by reference in itsentirety.

What is claimed is:
 1. An optical recording medium onto which recordinginformation can be recorded optically, comprising: a first area wherethe recording information is recorded on groove tracks formedmeanderingly so as to extract wobble signal; a second area where a phasepit string corresponding to control data required for reproductioncontrol of the recording information is arranged meanderingly, the phasepit string having a pit depth so that it enables the control data to beread and reading of other data overwritten on the phase pit string isprevented; and a third area where a phase pit string corresponding topredetermined data is arranged meanderingly, the phase pit string havinga pit depth so that it enables pre-pits including address informationrepresenting a recording position on said optical recording medium to beread and reading of other data overwritten on the phase pit string isprevented, wherein a meandering amplitude of said second area and ameandering amplitude of said third area are set so that output levels ofwobble signals extracted from said respective areas are approximatelyequal to an output level of the wobble signal extracted from said firstarea.
 2. The optical recording medium according to claim 1, wherein thepre-pits are formed at least on said first area and said third area. 3.The optical recording medium according to claim 2, wherein the pit depthon said third area is set so as to be equal to the depth of the groovetracks of said second area.
 4. The optical recording medium according toclaim 3, wherein on said first area, a depth of the groove tracks is setto 30 nm, on said second area, the pit depth is set to 80 nm, an averageduty of the pit string is set to approximately 50%, and the meanderingamplitude is set to be approximately 2.7 times as much as that of saidfirst area, and on the third area, the pit depth is set to 30 nm, anaverage duty of the pit string is approximately 80%, and the meanderingamplitude is set to be approximately 1.3 times as much as that of saidfirst area.
 5. The optical recording medium according to claim 2,wherein the meandering amplitude of said third area is set so as to beequal to the meandering amplitude of said first area.
 6. The opticalrecording medium according to claim 5, wherein on said first area, adepth of the groove tracks is set to 30 nm, on said second area, the pitdepth is set to 80 nm, an average duty of the pit string is set toapproximately 50%, and the meandering amplitude is set so as to beapproximately 2.7 times as much as that of said first area, and on saidthird area, the pit depth is set to 50 nm, an average duty of the pitstring is set to approximately 80%, and the meandering amplitude is setto be equal to that of said first area.
 7. An optical recording mediumproducing apparatus for producing an optical recording medium onto whichrecording information can be recorded optically using an optical discmaster, comprising: a first area forming device for cutting groovetracks meanderingly on said optical disc master using a light beammodulated by a wobble signal so as to form a first area onto which therecording information is recorded; a second area forming device formeanderingly cutting a phase pit string corresponding to control datarequired for reproduction control of the recording information on saidoptical disc master using the light beam modulated by the wobble signalso as to provide a pit depth which enables reading of the control dataand which prevents reading of other data overwritten on the phase pitstring, and for forming a second area; and a third area forming devicefor meanderingly cutting a phase pit string corresponding topredetermined data on said optical disc master using the light beammodulated by the wobble signal so as to provide a pit depth whichenables reading of pre-pits including address information representing arecording position on said optical recording medium and which preventsreading of other data overwritten on the phase pit string, and forforming a third area, wherein in said second area forming device andsaid third area forming device, a degree of modulation of the lightbeams due to the wobble signal is set so the output levels of wobblesignals extracted from said respective areas are approximately equal toan output level of the wobble signal extracted from said first area atthe time of reproduction from said optical recording medium produced byusing said optical disc master.
 8. The optical recording mediumproducing apparatus according to claim 7, wherein said first areaforming device and said third area forming device form the pre-pits. 9.An optical recording medium producing method for producing an opticalrecording medium onto which recording information can be recordedoptically using an optical disc master, said method comprising: a firstarea forming process of meanderingly cutting groove tracks on saidoptical disc master using a light beam modulated by a wobble signal soas to form a first area on which the recording information is recorded;a second area forming process of meanderingly cutting a phase pit stringcorresponding to control data required for reproduction control of therecording information on said optical disc master using the light beammodulated by the wobble signal so as to provide a pit depth whichenables reading of the control data and which prevents reading of otherdata overwritten on the phase pit string, and of forming a second area;and a third area forming process of meanderingly cutting a phase pitstring corresponding to predetermined data on said optical disc masterusing the light beam modulated by the wobble signal so as to provide apit depth which enables reading of pre-pits including addressinformation representing a recording position on said optical recordingmedium and which prevents reading of other data overwritten on the phasepit string, and of forming a third area, wherein at the second areaforming process and the third area forming step, a degree of modulationof the light beam due to the wobble signal is set so that output levelsof the wobble signals extracted from said respective areas areapproximately equal to an output level of the wobble signal extractedfrom said first area.
 10. The optical recording medium producing methodaccording to claim 9, wherein the first area forming process and thethird area forming process form the pre-pits.